Halep, seeded fifth, had the seventh-seeded Stosur on the defensive much for the day, piling up 18 break chances during her 7-6 (7-1), 6-2 victory. Halep converted one of her 12 break opportunities in the first set before taking the tiebreaker and finished off three of her six in the second for the win.
She ended up winning 51 percent (45-of-87) of the points off Stosur's serve while winning 62 percent on serve with a dropped service game in each set.
It was the fifth WTA championship for Halep, who won her first title in mid June. Counting that tournament win in Nuremberg, Germany, Halep is 35-6 in 11 events the second half of this year.
Only world No. 1 Serena Williams who's won 10 times this year, has more championships than Halep in 2013.
Halep is 5-3 overall in WTA finals. The first-place check of $132,470 pushed her career winnings to nearly $1.8 million. She's won more than $952,000 this year.
Stosur dropped to 5-13 in finals. She won events in Carlsbad, Calif., and -- last week -- in Osaka, Japan, this year. Stosur collected $70,728 as the runner-up Sunday. She's won about $12.7 million in her career.